Oscillator frequency regulation



July 13, 1937. D. w. M ILHINELY 2,036,919

OSCILLATOR FREQUENCY REGULATION Filed qul 31. 1935 I Carrier Source Frequencq 5 Modulator Amplifier Controller "LOCCZZ Oscillator Control Detector 7 Oscillaior ATTO RN EYS Patented July 13, 1937 UNITED STATES OSCILLATOR FREQUENCY REGULATION Donald W. McIlhiney, Great Neck, N. Y. Application July 31, 1935, Serial No. 33,943 1 Claim. (01. 2 50-20) This invention relates to frequency regulation of oscillators and has for an object to vary the output frequency of an oscillator in response to variation in the frequency of another source of alternating electrical energy.

According to the invention, electrical oscillations of one frequency are modulated by electrical oscillations of another frequency with re sulting sum and difference frequency oscillations. l The resulting oscillations are impressed upon an oscillator designed to oscillate at a frequency in the neighborhood of one of the sum or difference frequencies of such oscillations. For a limited range of frequencies above and below its natural oscillation frequency, the oscillator will fall into step with the impressed oscillations of the frequency nearest its natural oscillation frequency and supply alternating energy at the frequency of such impressed oscillations. Any change in the frequency of either of the original oscillations will result in a corresponding change in the output frequency of the oscillator. Thus, if one of the original oscillations is maintained at constant frequency, the output frequency of the oscillator is controlled entirely by the variation in the other original frequency.

Other objects, novel features and advantages of this invention will become apparent from the following specification and accompanying drawing, wherein;

The figure is a diagrammatic view of an apparatus embodying the invention.

In the illustrated apparatus are provided two different sources I and 2 of electrical oscillations.

. These sources of electrical oscillations are connected to a modulator 3 which may be any one of a number of different types which produce sum and difference frequency oscillations when supplied with two: or more electrical oscillations.

40 The output of the modulator 3 is impressed upon an oscillator consisting of a circuit 4 containing frequency controlling elements and an amplifier 5. The output of the oscillator is delivered at the terminal 6.

4 The various elements of the apparatus are all disclosed diagrammatically as the particular construction thereof is not involved in the present invention and these elements are all well-known in the art. The modulator and oscillator may 50 be of the well-known vacuum tube type, but

may also be of any other type which effects modulation of different frequency oscillations or which is operative to produce electrical oscillalI-IOIIS.

55 In operation, the frequency controlling circuit 4 is adjusted to produce oscillations of a frequency in the neighborhood of one of'the oscillations to. be produced by the modulator 3. The I impressing of oscillations of a frequency in the neighborhood of the frequency at which the oscil- 5 lator would oscillate if undisturbed by external voltages or currents, causes the oscillations of the oscillator to fall in step with the impressed oscillations. The result is to supply to the terminal 6 electrical oscillations, the frequency of which is 10 strictly under the control of the sources I and 2. The frequency of the electrical oscillations at the terminal 6 will be of the same stability as the combined stability of the sources I and 2.

Network or circuit elements may be inserted in the modulator 3 and/or in the frequency controlling circuit t which tend to permit one of the output oscillations of the modulator 3 to affect the oscillator to the exclusion of the other output oscillations of the modulator.

In a specific embodiment of the invention, the oscillator 45 may constitute the local oscillator in a superheterodyne radio receiver, the source l constitute the antenna of such receiver and the source 2 constitute a control oscillator adjusted to operate at the frequency of the intermediate frequency amplifier of the receiver. In this arrangement, the output of the local oscillator will be under the control of the incoming radio frequency carrier and the control oscillator operating at the intermediate frequency. As a result, adjustment of the frequency controlling circuit 4 is very simple as only an approximate adjustment is required. The terminal 5 constitutes the input for the first detector 1 of the superheter- 5 odyne radio receiver and the antenna i is connected tothe detector 1 in the usual manner.

To take a specific example, assume thatthe carrier wave which it is desired to receive is 1,000 kc. and that the intermediate frequency is 1'75 kc. and further assume that the local oscillator is intended to operate below the carrier frequency. The control oscillator 2 is then tuned to 1'75 kc. and the local oscillator is tuned to the neighborhood of 825 kc. The modulator 3 will supply oscillations having a frequency of '825 kc. and also oscillations having a frequency of 1175 kc. among others. The frequency of the output of the local oscillator is then under the control of the carrier waves and the frequency of osclllations supplied to the intermediate frequency amplifier as a result of the interaction between the local oscillator 4-5 and the incoming carrier is automatically maintained at the proper Value for optimum operation of the superheterodyne receiver, for if the incoming carrier varies in frequency corresponding variations will be produced in the frequency of the local oscillator with the result that the frequency supplied to the intermediate frequency amplifier will not vary.

Preferably, in the embodiment just described, the source 2 may be of such type that its variations of frequency with change of temperature Will be of the same nature as the variation in filtering action of the intermediate frequency amplifier produced by the same cause. This will result in the frequency supplied to the intermediate frequency amplifier varying in the same manner as the ability of the intermediate frequency amplifier to handle it.

I claim:

In a superheterodyne radio receiver, a first detector, a local oscillator, a control oscillator oscillating at the desired final intermediate frequency, a modulator, means for impressing incoming carrier oscillations and the output oscillations of said control oscillator upon said modulator, and for impressing the output of said modulator upon said local oscillator, said local oscillator being tuned to a frequency in the neighborhood of one output frequency of said modulator, and means for impressing the output of said local oscillator upon the input of said first detector.

DONALD W. MCILHINEY. 

